The erythrocyte membrane has proven to be an accessible and informative membrane system. The existence of related proteins in nonerythroid membranes attests to the general relevance of this model. Also, specific molecular defects have been identified which result in clinical anemias. The long term goals of this proposal are to explore the normal and pathological roles of two very recently identified integral membrane proteins and to evaluate variants of recognized membrane proteins found in certain congenital anemias. I. The clinically important Rh antigen system will be investigated at a molecular level by focusing upon the 30,000 Mr Rh associated integral membrane protein (Rh-IMP). Rh-IMPs purified from blood with specific Rh types will be analyzed for intrinsic differences in peptide composition. The importance of the covalent fatty acylations will be studied. Associations with other proteins and details of the specific membrane conformation required for surface immunogenicity will be investigated. II. The 28,000 Mr membrane-skeleton-linked integral membrane protein will be studied. The physical and chemical nature of the protein, the existence in nonerythroid cells, nature of the membrane-skeleton linkage, and potential physiologic functions will be investigated. III. The roles of protein 4.1 and spectrin will be analyzed in certain congenital anemias. The prevalence of 4.1 variants in ovalocytosis will be ascertained, and functional consequences of recently identified 4.1 variants will be measured. The role of spectrin in spherocytosis will be further evaluated.